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School of Biological and Behavioural Sciences

Liam Nash


PhD student



Project title: Spatial extent and impact of aquatic resources on terrestrial communities, individuals and trophic dynamics in tropical and temperate forests

Summary: Terrestrial communities and trophic dynamics are heavily impacted by inputs of aquatic resources, primarily in the form of emerging, adult, freshwater insects. However, it is not understood how far these impacts reach inland or whether there are any generalisable patterns across different biomes or latitude.

This project will use δ15N and δ13C stable isotope analysis with Bayesian analyses to track the impact of aquatic-terrestrial linkages away from aquatic sources, evaluating changes in the dietary breadth (and other isotopic metrics) of consumers at the community and species level along 150m transects away from streams. Community structure responses will be further evaluated, in terms of changes in α and β diversity, abundance and biomass between transect points, streams and sites. Through having a standardised method of sampling carried out in multiple sites in Brazil and Europe, comparisons between different climatic zones (tropical, temperate), forest types (Amazon, Atlantic rainforest, conifer plantation and broadleaf forest), and latitudes (Scotland to Atlantic Rainforest) can be made. Finally, the extensive dataset of ~700 sampled communities, from across two continents, will be used to develop a spatial model incorporating trophic dynamics and environmental parameters. This model will aim to estimate how wide riparian buffer zones need to be to encompass full cross-ecosystem dynamics, depending on geographic location, forest type and species compositions. The large dataset will be formatted, uploaded to a server and made available for future hypotheses to be explored.

As forests are increasingly cleared around the globe (but especially in the tropics) to make way for the needs of a growing human population, policy makers and environmental managers increasingly need to make informed decisions on where to prioritise conservation efforts. Riparian buffers are a commonly used to protect the forest-freshwater interface, but we lack knowledge of how wide they need to be to maintain healthy cross-ecosystem processes. Ultimately, this research aims to guide and inform policy specifically related to riparian buffers, but also to further understanding on how trophic interactions integrate different ecosystems within a whole, interconnected landscape.